For the recording of X- or gamma radiation, for example in X-ray computer tomography systems, so-called directly converting radiation detectors are known. Such radiation detectors generally comprise a plurality of detector modules, by which X-radiation is converted into electrical signals in a one-stage interaction process. To distinguish the terminology in this context, scintillator photodiode detectors for example are to be mentioned by which the radiation is converted into electrical signals in a two-stage interaction process: in a first interaction process, the radiation is converted into light by means of a scintillator. The light is in turn converted into electrical signals in a second interaction process by way of photodiodes.
Known directly converting detector modules include for example a plurality of detector submodules arranged successively in the manner of tiles, which include a converter layer made of a semiconductor material. Charges, specifically electron-hole pairs, are generated by interaction of the radiation with the semiconductor material i.e. by quantum absorption events. For spatially resolved recording of the charges, and therefore of the quantum absorption events, a multiplicity of pixel electrodes are provided on a first side of the converter layer and a counter-electrode or cover electrode is provided on a second side opposite to the first side, a voltage being applied between the counter-electrode and the pixel contacts. The counter-electrode or cover electrode is also known by the term back contact.
The voltage generates electrical fields in the converter layer, by which the charges are separated and—according to the type of charge—accelerated to the counter-electrode or to the pixel electrodes. The charges moved in this way induce currents on the corresponding electrodes, which can be recorded as electrical signals. With the aid of the electrical signals, it is possible to determine for example an attenuation image of an object to be examined.
In such detector modules, it is thus necessary to supply the electrodes with the corresponding voltage. This is problematic in several regards: it is necessary to ensure that the voltage supply to all the electrodes is of consistent quality. A difficulty with this is that a scattered radiation collimator is generally arranged on the counter-electrode side of the detector module. The scattered radiation collimator impedes accessibility to the counter-electrodes, so that the technical possibilities for contacting the counter-electrodes are significantly restricted. Since the voltage may lie in the kilovolt range, it is likewise desirable to ensure sufficient electrical insulation from other components of the radiation detector.